1. Field of the Invention
The present invention relates to lithographic apparatus, equipment, and methods.
2. Description of Related Art
A lithographic apparatus is a machine that applies a desired pattern onto a target portion of a substrate. Lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that circumstance, a lithographic patterning device, which is alternatively referred to as a “mask” or “reticle,” may be used to generate a circuit pattern corresponding to an individual layer of the IC, and this pattern can be imaged onto a target portion (e.g., comprising part of, one or several dies) on a substrate (e.g., a silicon wafer) that has a layer of radiation-sensitive material (i.e., resist).
In general, a single substrate will contain a network of adjacent target portions that are successively exposed. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion in one go, while in so-called scanners, each target portion is irradiated by scanning the pattern through the projection beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction.
The term “patterning device” used herein should be broadly interpreted as referring to a device that can be used to impart a projection beam with a pattern in its cross-section such as to create a pattern in a target portion of the substrate. It should be noted that the pattern imparted to the projection beam may not exactly correspond to the desired pattern in the target portion of the substrate. Generally, the pattern imparted to the projection beam will correspond to a particular functional layer in a device being created in the target portion, such as an integrated circuit.
The patterning device may be transmissive or reflective. Examples of patterning means include masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in lithography, and include mask types such as binary, alternating phase-shift, and attenuated phase-shift, as well as various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted so as to reflect an incoming radiation beam in different directions; in this manner, the reflected beam is patterned.
Generally, such patterning devices are transported from one location to another via a transport box, which are readily known and widely used. The transportation can take place between a stock of patterning devices and a lithographic apparatus. When the patterning devices are located inside the box, transportation is possible while the patterning devices are protected against outside contamination (e.g., organic contamination, Si-particles, metal particles, chemical contamination, molecular contamination, dust particles, etc.).
After transportation, the patterning devices can be transferred from the box to the lithographic apparatus. Afterwards, further transportation is performed by a pick and place machine (i.e., placing equipment) to a reticle stage/table/holder that holds the patterning device while an exposure beam of radiation exposes substrates or wafers.
According to a conventional method of exchanging patterning devices, the transport box loaded with the patterning device is coupled to the lithographic apparatus. The coupling is facilitated by an arrangement in which a door of the box, carrying the patterning device, is coupled to a door of the lithographic apparatus that is, in turn, coupled to an elevator mechanism. After the coupling, the elevator with the doors is lowered and the patterning device enters the lithographic apparatus for further transport into the reticle stage.